Thanks for all the help. I'm talking a about a ceiling mounted system, so the temperature of the welding products is not an issue.

I'm helping outfit a new metal shop with an air filtration system. The wood shop next door has a Jet AFS-2000 ceiling mounted air filtration unit that we bought used, in addition to a full dust collection system throughout the shop. I see that the Jet warranty is void if these units are used anywher...

Bill[/quote] What goes out has to come in from somewhere. To get maximum efficiency from a fan there must be an adequate inlet air supply from somewhere. The "747" is just the poor fan working its butt off with no air to feed it. ;) Try opening a window or door a bit and see what happens.[...

It's not a house. It's a metal shop, 30' L x 18' W x 15' H. The welding bench is at one end of the shop, and we're going to vent the fan to the outside. Venting is necessary to pass inspection. I'm still struggling to find a number SOMEWHERE that says - for MIG welding, you need a minimum of X cfm t...

Oscar, this is the bigger version of the one I saw listed from Harbor Freight for $80.

Thanks to all for the great info. I guess the thing I was missing was the difference in power. As I understand it, the higher the motor power, the better the machine can overcome a given static pressure drop to deliver a desired flow rate. The $470 Dayton 10" roof ventilator is 0.125 hp, while ...

Thanks for the excellent tips, MinnesotaDave. We're planning to design and build our own hoods and vent to the outside, rather than use a machine like the one you showed. I see prices all over the place. There's an $80 ventilation fan from Harbor Freight that is 1590 cfm: https://www.harborfreight.c...

I'm helping my son who is building a new makerspace (a collaborative work space) that includes a metal shop. There will be three MIG stations along one wall, and he asked me to design a fume extraction system. (I'm a retired mechanical engineer.) I'm thinking of either a single hood along the wall, ...